Postulates for safety requirements

The engineering work of the architect consists of identifying a coherent and comprehensive list of properties ensuring dependability [VIL 88] of the PIPC generic platform. 

The resulting safety concepts are defined with regards to the following safety requirements  

These safely requirements conceptually have two strong limitations  

Obviously, there is another demonstrable limit of a safety level. This limit depends on the devil s hand . This is not a philosophical approach but a matter of safety culture . Some believe that if a failure scenario (failure mode) cannot be proven not to occur, then by hypothesis, it will certainly occur (with a probabihty equal to 1). Others believe the opposite it is pointless to consider a failure scenario (failure mode) whose existence cannot even be technically proven. 

In the railway domain, the development of the software must conform to the European standard CENELEC 50128 [CENOl], For the most critical software, the developmental, validation and verification process is of SIL 4 level. 

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